LYNCHBURG, Va. (AP) — Mitt Romney's Mormon faith has shaped his life, but he barely mentioned it as he spoke to graduates at an evangelical university Saturday.

And he hardly touched on hot-button social issues like abortion and gay marriage, instead offering a broad-based defense of values like family and hard work.

"Culture — what you believe, what you value, how you live — matters," Romney told graduates gathered in the football stadium on Liberty University's campus in the Virginia mountains. "The American culture promotes personal responsibility, the dignity of work, the value of education, the merit of service, devotion to a purpose greater than self, and at the foundation, the preeminence of the family."

Instead of a red-meat conservative policy speech, Romney discussed his own family and offered a defense of Christianity, saying that "there is no greater force for good in the nation than Christian conscience in action." Still, he was inclusive: "Men and women of every faith, and good people with none at all, sincerely strive to do right and lead a purpose-driven life," Romney said.

He had one sustained applause line in a 20-minute speech delivered days after President Barack Obama historically embraced gay marriage. "Marriage is a relationship between one man and one woman," Romney said to a cheering crowd of students who have to follow a strict code of conduct that considers sex out of wedlock and homosexuality to be sins.

On Saturday, Obama was not seeking to revisit the issue of gay marriage. In his weekly radio and Internet address, the president didn't mention his history-making endorsement. Instead, he repeated his call for congressional lawmakers to take up a "to-do list" of tax breaks, mortgage relief and other initiatives that he insists will create jobs and help middle-class families struggling in the sluggish economy.

Having spent part of the week on the West Coast raising money for his re-election effort, Obama appeared in the Rose Garden of the White House to honor award-winning law enforcement officers.

It was Obama's first joint appearance with Vice President Joe Biden after Biden, according to aides, apologized to the president for pushing gay marriage to the forefront of the presidential campaign and inadvertently pressuring Obama to declare his support for same-sex unions.

Obama and Biden were all smiles as they walked to the sun-splashed ceremony together. Introducing Obama, Biden credited the president's commitment to law enforcement and the two quickly embraced before Obama spoke.

The late Rev. Jerry Falwell founded Liberty University in 1971 to be for evangelical Christians "what Notre Dame is to young Catholics and Brigham Young is to young Mormons," as his son, University Chancellor Jerry Falwell Jr., said on commencement day. It's become a destination for Republican politicians looking to speak to the religious right, and Romney's campaign team — planning the speech long before gay marriage became a central issue — viewed it as an opportunity to address the kind of socially conservative audience that had been wary of him during the prolonged GOP primary fight.

For Romney, the challenge is twofold. His past policy positions, including support for abortion rights, don't sit well. But his personal faith is also an issue because many evangelicals don't consider Mormons to be fellow Christians. Evangelicals are a critical segment of the GOP base; many of those voters backed his GOP rivals in the prolonged primary.

When he locks in the Republican presidential nomination, Romney will make history as the first Mormon nominee from a major party. His faith is central to him and to his family — he spent two years in France as a missionary, a time when he lived in occasionally primitive conditions. When he returned home, he attended Brigham Young University, a Mormon school, and married his wife, Ann, who had converted to Mormonism. As they built a life in Boston, Romney took on a significant leadership role in the church, serving as a lay pastor, fighting to build a temple in town and counseling families in need.

But he's mostly avoided talking about it on the campaign trail, largely avoiding religious forums and events throughout the primary season.

And at arguably the most religious venue he's addressed during the campaign — since announcing his bid, Romney hasn't made a public appearance in a church of any kind — he continued to keep his own faith in the background.

"This isn't a speech about Mormonism," senior adviser Eric Fehrnstrom told reporters Friday on a conference call. Fehrnstrom pointed to the speech Romney gave in Texas in 2007 outlining his faith and defending religious freedom — the last time the former Massachusetts governor has addressed his faith in any detail.

Still, it was clear the campaign was keenly aware of the overtones. Romney was introduced by Mark DeMoss, an evangelical who has repeatedly defended Romney's faith on the campaign trail. "I suspect I won't agree with Mitt Romney on everything, but I will tell you this: I trust him. I trust him to do the right thing," said DeMoss, who went on with a lengthy testament to Romney's values.

Despite the concern, surveys have shown for months now that whatever reservations Republican evangelicals have about Romney's faith, they are likely to back him in a general election.

A spokesman for Liberty said that Romney is not the first Mormon to speak at a university commencement. "This is our 39th commencement speaker, and 21 of those 39 speakers would not necessarily meet Liberty's doctrinal theological statement," said the spokesman, Johnnie Moore, explaining that anyone who teaches at the university is held to that doctrinal standard.

Romney's selection as commencement speaker was an issue for some students who graduated from Liberty this weekend. When the school announced Romney as commencement speaker, hundreds of angry comments were posted on Liberty's Facebook page by people who said they were students or alumni, objecting to giving a Mormon a platform. The school responded by affirming its welcome to Romney.

"There was some concern in my family, yes," because of Romney's Mormonism, said Robert Maginnis, a retired Army colonel whose nephew is a member of the 2012 class.

Ahead of Romney's remarks, University Chancellor Jerry Falwell Jr. said the school's invitation to him should not be considered an endorsement. He noted that his father, the school's founder, said that Christians should vote for the candidate who shares their political positions "not the candidate that shares his or her faith or theology."

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Zoll reported from New York. Associated Press writer Ken Thomas in Washington contributed to this report.